Over time, the stored fruits and vegetables will evaporate a certain amount of water. The control system will automatically increase the humidity according to the humidity in the storehouse detected by the humidity sensor until it reaches the set requirements. The air-conditioning and fresh-keeping is completed by the air-conditioning machine (hereinafter referred to as the air-conditioning machine). In addition, the control system also periodically and automatically fills the warehouse with ozone to sterilize fruits and vegetables.
The selection of control hardware and the preparation of software are to simplify the system, facilitate maintenance, improve the reliability of the system and the on-site response capability, and achieve the multi-control of one machine (that is, one air-conditioning machine controls multiple warehouses), and the core hardware of gas regulation and preservation Adopt PLC. PLC has strong I / O control ability, good at logic analysis and control. After comparison, the system selected S7-200-CPU214), and additionally installed the expansion module S7-200-EM223.
The system control software can be compiled on the PC with the help of STEP-7MicroWin32 software provided by SIEMENS, and then the RS232 communication port on the PC is connected to the PLC to download the compiled software to the PLC to control the operation of the system.
Features of PLC control system for gas conditioning and preservation After PLC control is adopted for gas regulation and preservation, in addition to the simple and clear internal connection of the air conditioner and the simple and beautiful operation panel, it also has the following features. Two warehouses share a temperature and humidity secondary meter and an oxygen content secondary meter, which saves costs. Only one button (no mechanical self-locking) pair of contacts can realize the system start / stop function. It has realized that one air-conditioning machine can automatically control the preservation operation of two warehouses at the same time (or separately). The control process can be modified flexibly according to the variety of freshness.
The normal operation of the system shows that the gas-regulated fresh-keeping system controlled by PLC is designed correctly and the operation is stable and reliable. LD11 aluminum skirt adopts isothermal forging process to achieve one-shot forming, and can obtain good mechanical properties after CS treatment. The isothermal compression test performed on the material of the hot extruded rod after CS treatment showed that: under the deformation test conditions of temperature 480 ℃ and strain rate 0.005 ～ 0.01 / s, the material will exhibit superplastic effect, and its plasticity needs further verification .
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